// 檢測port是否被占用function probe(port, callback) {  var server = net.createServer().listen(port)  var calledOnce = false  var timeoutRef = setTimeout(function () {    calledOnce = true    callback(false,port)  }, 2000)  timeoutRef.unref()  var connected = false  server.on('listening', function() {    clearTimeout(timeoutRef)    if (server)      server.close()    if (!calledOnce) {      calledOnce = true      callback(true,port)    }  })  server.on('error', function(err) {    clearTimeout(timeoutRef)    var result = true    if (err.code === 'EADDRINUSE')      result = false    if (!calledOnce) {      calledOnce = true      callback(result,port)    }  })}function server(_port){  var pt = _port || __port;  probe(pt,function(bl,_pt){    // 端口被占用 bl 返回false    // _pt：傳入的端口號    if(bl === true){      // ssr(_pt)      server = http.createServer(connListener);      server = server.listen(parseInt(_pt, 10));      console.log("/n Static file server running at" + "/n/n=> http://localhost:" + _pt + '/n');    }else{      server(_pt+1)    }  })}